1. Field of the Invention
The present invention relates to a navigation apparatus, and more particularly to a navigation apparatus which displays a map together with information concerning facilities and the like around a user""s location.
2. Description of the Background Art
A primary purpose of a navigation apparatus is to compute a route to a destination and display the computed route. Some navigation apparatuses display, together with the computed route to the destination, various information which is useful for the user. For example, a navigation apparatus has been proposed which displays various facilities (e.g., gas stations, restaurants, and the like) which are in the neighborhood of the current location of a vehicle incorporating the navigation apparatus (hereinafter simply referred to as xe2x80x9cthe vehiclexe2x80x9d). In the following description, information on facilities which are in the neighborhood of the vehicle, as displayed by the navigation apparatus, will be referred to as xe2x80x9cfacility informationxe2x80x9d.
One example of a conventional navigation apparatus capable of displaying the aforementioned facility information computes a distance (or the like) from a current location to each facility which is present along a predetermined road, and generates a table containing information concerning such facilities. FIG. 22 shows an exemplary image displayed by such a navigation apparatus. As shown in FIG. 22, the following information is displayed: facilities (e.g., C1, R1, and G1) which are present along a predetermined road, distances (e.g., 2 km, 3 km, and 5 km) to the facilities, and which side of the road each facility is located. Thus, with respect to facilities which are present along the predetermined road, the user can easily ascertain their locations, distances thereto, and the like.
Another example of a conventional navigation apparatus looks for, when a route has been set, facilities which are present within a certain distance from the route, and displays information concerning such facilities. The user is thus enabled to easily obtain information concerning facilities in the neighborhood of the route.
As described above, the conventional technique which displays the exemplary image as shown in FIG. 22 displays information concerning facilities present along a predetermined road. However, this technique only makes it possible to obtain information concerning facilities which are present along the predetermined road. No facility information can be obtained for any roads other than the predetermined road, even for roads which lie generally in the traveling direction of the vehicle. Therefore, the user cannot obtain facility information concerning any other roads branching from the predetermined road. For example, if the user wishes to visit a gas station while traveling along a route to a destination, the navigation apparatus will not display any gas station information unless there is a gas station which is along the route to the destination. Therefore, the user cannot obtain information on any gas station which is located along a road branching off from the route to the destination.
The other conventional technique which looks for facilities which are present within a certain distance from the route and displays screen information on the found facilities as a separate image allows the user to know the existence of facilities which are in the neighborhood of the route. However, with this technique, it is impossible for the user to obtain detailed information concerning the facilities, e.g., which intersection to turn in order to arrive at a facility, or the travel distance and estimated travel time before arriving at the facility. Moreover, this technique assumes that a route has been set, so that it is impossible to look for such facilities unless a route has been set.
Thus, the above-described two conventional techniques, which display information related to a preselected road or the neighborhood thereof, the user may not necessarily be able to obtain sufficient information concerning facilities lying ahead of the user along his/her traveling path.
Therefore, an object of the present invention is to provide a navigation apparatus which provides a user with information concerning facilities or the like which are present in a broad range ahead of the user, such information being displayed in a comprehensible manner.
The present invention has the following features to attain the object mentioned above.
A first aspect of the present invention is directed to a navigation apparatus for displaying a road map on a screen of a display device, comprising a map data storage section, a moving state acquisition section, a reference intersection selection section, a point information acquisition section, and a map displaying section. The map data storage section stores map data including point information concerning points on the map. The moving state acquisition section acquires a location and a traveling direction of a user. The reference intersection selection section selects, from among intersections displayed on the screen, at least one intersection included in a network of roads extending from the location of the user in the traveling direction as a reference intersection. As used herein, the location of a user is a notion which encompasses a virtual location of the user, as well as the current location of the user. The point information acquisition section acquires, from the map data storage section, point information concerning a point near a road in a network of roads extending beyond a reference road as seen from the reference intersection, wherein the reference road is a road which is connected to the reference intersection but does not extend toward the location of the user from the reference intersection. Alternatively, roads extending toward the current location from the reference intersection may also be designated as reference roads. The map displaying section displays the road map, and displays the point information acquired by the point information acquisition section so as to appear associated with the reference road associated with the point information.
According to the first aspect, point information concerning a point existing beyond an intersection located ahead of the user (reference intersection) is displayed so as to appear associated with a road connected to the intersection (reference road) (see FIG. 10). As used herein, the xe2x80x9cpoint informationxe2x80x9d is information concerning a point on the map, and is a notion encompassing facility information concerning facilities and information such as names of places. Thus, the user can immediately understand what lies beyond each road connected to an intersection which is located ahead of the user. In other words, with respect to each piece of point information displayed on the screen, the user can immediately understand which way to turn at which intersection. Since it is possible to display point information for a plurality of roads connected to a reference intersection, the user can obtain point information concerning points in a broad area range ahead of the user.
In the first aspect, the navigation apparatus may further comprise a network computation section for computing a search network, wherein the search network is the network of roads extending beyond the reference road as seen from the reference intersection, wherein, the point information acquisition section acquires point information concerning a point near a road in the search network as the point information associated with the reference road.
In the first aspect, the network computation section may select only a predetermined category of roads in the map data for the search network. Thus, a search network composed only of major roads such as national and/or prefectural roads can be defined. In this case, only the point information concerning points which are present near major roads is displayed on the display device. Since the user is generally believed not to travel along roads other than the major roads in unfamiliar places, displaying only point information near the major roads can provide a sufficient advantage in displaying point information over a broad range. By excluding roads other than the major roads from the search network, the search network computation process can be simplified. As a result, the processing time need to display point information can be reduced.
In the first aspect, the point information acquisition section may comprise a condition checking section for determining, if point information is redundantly acquired as a result of acquiring point information associated with a plurality of said reference roads, whether or not each of the plurality of reference roads associated with the point information which has been redundantly acquired satisfies a predetermined condition based on the search network, and the map displaying section may display the point information redundantly acquired by the point information acquisition section so as to appear associated with those reference roads which are determined by the condition checking section as satisfying the predetermined condition.
Thus, even if the same point information is redundantly acquired, not all of the acquired pieces of point information are displayed. In a method where point information is acquired by using a search network, especially in the case where there are a plurality of reference intersections, the same point information may be redundantly acquired, so that the point information concerning the same point may be displayed in connection with a plurality of reference roads, thus making it difficult for the user to judge which reference road the user should choose to arrive at the point. Conversely, by ensuring that the point information is displayed only in connection with reference roads which satisfy the predetermined condition, it becomes possible to reduce the number of pieces of point information displayed on the screen, thus facilitating the judgement by the user. Since unnecessary point information is not displayed, the displayed image on the screen is easier to see.
The predetermined condition may be a condition concerning the distance of a path from the reference intersection to a point represented by the point information via the reference road, and the condition checking section may determine, by computing the distance with respect to each of the plurality of reference roads using the search network, whether each of the plurality of reference roads satisfies the predetermined condition or not. Thus, assuming that the predetermined condition stipulates xe2x80x9ca reference road included in a path which constitutes the smallest distance from a reference intersection to a pointxe2x80x9d, for example, point information is displayed only with respect to reference roads included in a path which constitutes the smallest distance from the reference intersection to the point, so that no point information is displayed with respect to the other unnecessary reference roads. As a result, the user can know the shortest path to the point without having to choose from a number of reference roads to take.
The predetermined condition may be a condition concerning an estimated travel time for a path from the reference intersection to the point represented by the point information via the reference road, and the condition checking section may determine, by computing the estimated travel time for each of the plurality of reference roads using the search network, whether each of the plurality of reference roads satisfies the predetermined condition or not. Thus, assuming that the predetermined condition stipulates xe2x80x9ca reference road included in a path which imposes the shortest estimated travel time from a reference intersection to a pointxe2x80x9d, for example, point information is displayed only with respect to reference roads included in a path which imposes the shortest estimated travel time from the reference intersection to the point, so that no point information is displayed with respect to the other unnecessary reference roads. As a result, the user can know the least time-consuming path to the point without having to choose from a number of reference roads to take.
In the case where the condition checking section is comprised, the navigation apparatus may further comprise a road history storage section for storing a history of roads traveled along in the past, wherein, the predetermined condition is a condition concerning the history of roads, and the condition checking section determines whether each of the plurality of said reference roads satisfies the predetermined condition, based on a relationship between the search network and history of roads stored in the road history storage section.
Thus, point information is displayed only with respect to reference roads included in a path which includes roads which has previously been traveled along, so that no point information is displayed with respect to the other reference roads. There is a relatively low possibility for the user to get lost on a road which the user has traveled along before, and thus a relatively low possibility for missing a desired point. Therefore, by displaying point information only with respect to reference roads which have previously been traveled along, it becomes possible to exclusively display paths which are of high necessity to the user (i.e., highly likely to be selected by the user).
In the first aspect, the map data storage section may store map data in which each piece of the point information is associated with a road near the point corresponding to the piece of the point information, and the point information acquisition section may acquire the point information associated with the road in the map data as the point information concerning the point near the road.
Thus, it is possible to acquire point information by referring to the roads associated therewith, thereby facilitating the acquisition of point information concerning points in the neighborhood of the network of roads.
In the first aspect, the map data storage section may store map data including location information of the points, and the point information acquisition section may acquire point information concerning a point such that the distance between one of the roads in the search network and the point is equal to or less than a predetermined distance as the point information concerning the point near the road.
Thus, by using location information of points, point information for points which are included in the network of roads can be identified as the point information to be acquired. In this case, without the need to prepare map data in which point information is associated with roads, it is possible to acquire point information concerning points in the neighborhood of the network of roads.
In the first aspect, the navigation apparatus may further comprise a predicted road determination section for determining a predicted road from among the roads displayed on the screen, the predicted road being a road which the user is expected to travel along, wherein the reference intersection selection section selects the reference intersection from among intersections on the predicted road.
In the case where the predicted road determination section is comprised, the predicted road determination section may determine a route from a start point to a destination as the predicted road. Thus, a route to a destination is used as the predicted road, so that it is possible to accurately determine the road which is expected to be traveled along by the user.
In the case where the predicted road determination section is comprised, based on the location and the traveling direction of the user, the predicted road determination section may determine a road which lies in the traveling direction of the user and belongs to a predetermined road category as the predicted road. Thus, a major road such as a national or prefectural road can be used as a predicted road. In general, there is a higher expectation for the user to travel along major roads than lesser roads. Therefore, even in the case where no route has been selected, it is still possible to predict a road which the user is expected to travel along by determining a predicted road based on a predetermined road category.
In the case where the predicted road determination section is comprised, based on the location and the traveling direction of the user, the reference intersection selection section may determine an intersection on the predicted road that is closest to the location of the user as the reference intersection. There is a very high likelihood for the user to travel along an intersection on the predicted road that is closest to the current location. Therefore, by selecting such an intersection as the reference intersection, it becomes possible to display point information which is useful to the user.
In the case where the predicted road determination section is comprised, the reference intersection selection section may select as the reference intersection an intersection which is on the predicted road and at which a road belonging to a predetermined category connects to the predicted road. Thus, an intersection at which the predicted road connects to a road of a predetermined category, e.g., a major road such as a national or prefectural road is selected as the reference intersection. Since there is generally a high likelihood for the user to travel along a major road such as a national or prefectural road, it is also considered highly likely for the user to turn at an intersection which connects to such a major road. Therefore, by selecting such an intersection as the reference intersection, it becomes possible to display point information which is useful to the user.
In the case where the predicted road determination section is comprised, the navigation apparatus may further comprise a road history storage section for storing a history of roads traveled along in the past, wherein, based on the history of roads stored in the road history storage section, the reference intersection selection section selects as the reference intersection an intersection which is on the predicted road and at which a road stored in the road history storage section connects to the predicted road. Thus, an intersection at which the predicted road connects to a road which has previously been traveled along is selected as the reference intersection. It is also considered highly likely for the user to travel along a road which the user has previously traveled along. Therefore, by selecting such an intersection as the reference intersection, it becomes possible to display point information which is useful to the user.
In the first aspect, the point information acquisition section may acquire, from among the point information included in the map data, only a predetermined type of point information.
Thus, only a predetermined type of point information is displayed. Therefore, by setting the type of information to be displayed based on a certain condition (e.g., by allowing the user to preset the type of information in advance), it becomes possible to selectively display a desired type of information.
In the first aspect, the map displaying section may display the point information in an arrow shape oriented in an opposite direction from the reference intersection. Thus, the traveling direction can be indicated to the user. Moreover, the point information acquisition section may acquire a plurality of pieces of point information of different types, and the map displaying section may display the point information in different shapes depending on the types of point information. Thus, the user can easily grasp different types of point information.
A second aspect of the present invention is directed to a point information displaying method for displaying point information on a road map displayed on a screen of a display device, comprising the steps of: selecting, from among intersections displayed on the screen, at least one intersection included in a network of roads extending from a location of a user in a traveling direction of the user as a reference intersection, designating, as a reference road, a road which is connected to the reference intersection but does not extend toward the location of the user from the reference intersection; and displaying point information concerning a point near a road in a network of roads extending beyond the reference road as seen from the reference intersection so as to appear associated with the reference road. Alternatively, roads extending toward the current location from the reference intersection may also be designated as reference roads. By the above method, effects similar to those obtained according to the first aspect can be obtained.
A third aspect of the present invention is directed to a program for causing a computer to display a road map on a screen of a display device, wherein the computer stores map data including point information concerning points on the map, the method comprising: a moving state acquisition step of acquiring a location and a traveling direction of a user; a reference intersection selection step of selecting, from among intersections displayed on the screen, at least one intersection included in a network of roads extending from the location of the user in the traveling direction as a reference intersection; a point information acquisition step of acquiring, from the map, point information concerning a point near a road in a network of roads extending beyond a reference road as seen from the reference intersection, wherein the reference road is a road which is connected to the reference intersection but does not extend toward the location of the user from the reference intersection; and a map displaying step of displaying the road map on the display device, and displaying the point information acquired by the point information acquisition step so as to appear associated with the reference road associated with the point information. By allowing a computer to execute the program, effects similar to those obtained according to the first aspect can be obtained.
Thus, the third aspect can be implemented as a program, which can be transferred as recorded on a recording medium, thereby making it possible to implement the third aspect on another separate computer system.